Also, try the laptop. If that doesn't work after you totally uninstall the drivers and RSD Lite on your other box, reboot the computer, run a good reg cleaner (ccleaner), reboot, reinstall drivers and RSD, reboot, the plug your phone in normally and let the regular drivers install. Then boot your phone into bootloader and fire up RSD and let the flash interface drivers install. Or find a winXP box.
And the only thing wrong with rom manager is the people using it. I have NEVER EVER EVER had a problem with it in the whole time I have used it, and that is since it came out.